It is known that blends of linear low polyethylene (LLDPE) and polypropylene (PP) have improved stiffness (higher modulus) than LLDPE alone. Such blends exhibit a catastrophic decrease in impact and in tear strength, particularly in the machine direction (MD). We have found that LLDPE/PP blends containing minor amounts of an ethylene-propylene-diene monomer rubber (EPDM) or ethylene-propylene rubber (EPR) have the expected increase in stiffness along with unexpectedly improved MD Elmendorf tear and dart drop impact properties.
Certain blends of high pressure polyethylene, polypropylene and EPDM are described in U.S. Pat. No. 4,088,714 but these compositions contain a much higher EPDM content of (20 to 50 weight percent) than necessary in this invention.